For example, to find the sequence An, if the result of calculating An is similar to An = i.A(n- 1)+j, that is, the value of An is only related to a (n- 1), then use the first induction method (prove that n= 1 holds, let n=k hold, and find n = If it is similar to an = I a (n- 1)+j a (n-2)+m, that is, there are two or more correlations, then the second induction method is used (if n= 1 and 2 are both true, let n